The present invention relates generally to converter circuits. More particularly, the present invention relates to a DC-DC charge pump voltage converter-regulator circuit.
Many DC powered devices have subsystems that require a supply voltage higher than power supply can provide. For example, certain display devices that use liquid crystal technology require a relatively high voltage to operate. In these devices, the supply voltage is boosted in order to reach the required operating voltage. Various circuits may be used to do a DC-DC boost conversion of the supply voltage.
One method to obtain a regulated supply voltage for subsystems is to use switched capacitors voltage multipliers followed by a linear voltage regulator. The switched capacitors voltage multipliers multiply the supply voltage by a specified multiplication factor. For example, a supply voltage of 5 volts may be multiplied by a multiplication factor of 2 to achieve an output voltage of 10 volts. The linear regulator can then regulate the output voltage at any voltage level 10 volts or less.
The present invention is directed to converter circuits. More particularly, the present invention relates to a DC-DC charge pump voltage converter-regulator. The converter-regulator of the present invention includes improved efficiency by providing other forms of regulation for the output voltage. In one embodiment, the converter-regulator includes charge level control implemented by a flip-flop circuit. In a second embodiment, the control of the output voltage is implemented by a logic circuit. In a third embodiment, the control of the output voltage is implemented by an oscillator circuit. In a fourth embodiment, the control of the output voltage is implemented by multiplying the supply voltage according to a multiplication factor dependent upon the level of the supply voltage.
Briefly stated, an apparatus and method for a DC-DC charge pump voltage converter-regulator circuit includes a control circuit, a multiplier circuit, and a feedback circuit. The feedback circuit includes a load circuit, a comparator circuit, and a voltage reference circuit. The multiplier circuit produces an output signal by multiplying a supply signal according to a multiplication factor. The output signal is communicated to the load circuit. The output signal is measured producing a sense signal. The voltage reference circuit produces a reference voltage. The control circuit regulates the output signal according the result of a comparison between the sense signal and the reference voltage. In one embodiment, the multiplication factor is adjusted to compensate for a change in the supply signal. The multiplication factor may be increased to compensate for a decrease in the supply signal.
A more complete appreciation of the present invention and its improvements can be obtained by reference to the accompanying drawings, which are briefly summarized below, to the following detailed description of illustrative embodiments of the invention, and to the appended claims.